MIKE 21 BW - Numerical damping

Reference Manual
184 MIKE 21 BW - © DHI
The minimum wave period that can be modelled with and without the deep
water terms is shown in the table below.
(5.21)
5.5.14 Numerical damping
The figures below illustrate the influence of numerical damping on the signifi-
cant wave height in case of a practical application involving two generation
lines and the deep-water terms (enhanced Boussinesq equation).
The model setup is identical to the Hanstholm Harbour example enclosed in
the installation.
The first panel shows the result of a simulation with time-extrapolation
(default in MIKE 21 BW, time-extrapolation factor = 1). On the second panel
the time-extrapolation has been omitted corresponding to a backward time-
centring of the cross-terms (time-extrapolation factor = 0). Finally, the third
panel shows the results of using a mixture, i.e. time-extrapolation factor = 0.5.
A spatial constant time-extrapolation factor has been used.
The figures clearly illustrate the numerical damping when full or partly back-
ward time-centring of the cross-Boussinesq terms is applied all over the com-
putational domain.
Including
Deep Water Terms
Excluding
Deep Water Terms
Max. h/L
0
*0.5 0.22
Min. L
0
40 m 91 m
Min. Wave Period, Tmin 5.1 s 7.6 s
*L
0
gT
2
2
---------
1.56T
2
=